As semiconductor wafer processing moves toward the flexibility of single wafer processing, the ability to accurately measure and control the process and wafer state parameters becomes increasingly important. One of the most important parameters that need to be accurately monitored and controlled is wafer temperature. Currently, a majority of thermally activated single wafer processes such as rapid thermal processes rely on pyrometric temperature measurements. Pyrometric measurement, however, has several limitations. One of the most important limitations is that the temperature measurements are dependent on the emissivity of the wafer. The emissivity is a function of various wafer states including film material/thickness, substrate doping, and backside roughness. It is also strongly dependent on temperature. Thus, there is a need to correct the pyrometric temperature measurement for emissivity.